The present invention relates to a process for binding aggregates with a vacuum-activated catalyst. The invention is generally related to the preparation of a binder suitable for use in foundry, which binder is obtained when a resin is reacted with a blocked catalyst, the unblocking of which is achieved under vacuum.
The invention is mainly applicable to the manufacture of cores and molds, following an absolutely original technique in this field which results in remarkable economic, hygienic and cleaning advantages when compared with the system normally used.
In fact, in the foundry industry, metals, molds and cores are cast by mixing an aggregate, generally silica, although zirconium, olivinic, and other oxides can also be used, with binders. Hardening of these binders takes place with the help of a suitable catalyst and by supplying the case or mold with heat which has been introduced therein by the normal methods of blowing, firing, pouring, etc.
However, in the case of other binders which harden by cooling, a gaseous catalyst should be supplied to produce polymerization of the binder, i.e. hardening thereof.
The main disadvantages of these processes, clearly the most commonly used, reside in that when the catalyst is activated by supplying heat, there is a high consumption of energy. In the other case, when the catalyst is injected in the form of gas, which gas can normally be more or less harmful, the atmosphere in the working zone becomes unpleasant, and even dangerous, if the necessary safety measures are not adopted.